Below the fold... it's a term borrowed from newspaper advertising. When a broad sheet newspaper was folded in half and then stacked on a newsstand, you could only see the top half of the front page. Everything else was, well... below the fold.

The internet has borrowed this term to describe ads which are on the web page being browsed, but not visible unless the user scrolls down, and there has been a lot of talk over the past few months about whether Google should count an ad which is never seen as an impression. It's along the lines of trees falling in forests and no one hearing them....

A recent study has shown that almost 30% of all ads appear below the fold, and, of course, if you are paying for your ads on a CPM (Cost per Thousand impressions) basis, then you are paying for those ads - 300 in every thousand, which are never seen. Google announced that they were only going to count an impression if the ad had become visible through the user scrolling down the page. and this is where things get both interesting, and a little cloudy.

There is an option within the AdWords settings to exclude ad placements that are below the fold. This would seem like the ideal solution. Since we're not sure whether a visitor is ever likely to see the ad, we can simply exclude them - problem solved. Or is it?

Let's think about this for a moment. A user who scrolls down a page is likely to be much more engaged with that page's content than one who only looks at what is loaded into the initial viewport. And I would target the engaged user very time.

If I am paying on a CPM basis and Google are going to charge me for these "invisible" impressions - I'm going to exclude them.

But - I hear you shout - if you're paying on a CPC (Pay per Click) basis, then you only pay if a user clicks on your ad. If they don't see it - they can't click on it - you don't have to pay. And this is true. But it is also true that my CTR is being affected by the 30% of impressions that continue to be below the fold - and this will drag my CTR down disproportionately.

Until Google can assure us that we are only paying for ads below the fold when they become visible, it's a real dilemma.

What do you do? Do you exclude ad placements below the fold? If so, why - and, if not, why not?